Temperature independent timing device, dashpot type



May 11, 1965 TEMPE T y 1965 w. HARRIS ETAL 3,182,594

TEMPERATURE INDEPENDENT TIMING DEViCE, DASHPOT TYPE Filed May 17, 1965 V2 Sheets-Sheet 2 RETURN SP R|NG 25 KFIRING SOLENOID 24 MlGRO-SWITCH 23"PLUNGER SIMULATING BORE RIDING PIN 26 M-52A FUZE BODY IO F=Lun|sERMOVED BY SLIDER 9 -AcRo SWITCH 30 ,-'-SPRING LOADED RESET PLUNGER 33'LL=-RESETSOLENOID 3| FIG. 3.

' INVENTORS HARRY M. DAY 3 WI BUR HARRIS the lower temperatures.

3,1825% Patented May 11, 1965 3,182,594 TEMPERATURE INDEPENDENT TIMINGDEVICE, DASHPOT TYPE Wilbur Harris, Waukesha, Wis., and Harry M. Day,New

Canaan, Conn, assignors, by mesne assignments, to the United States atAmerica as represented by the decretary of the Army Filed May 17, 1963,Ser. No. 281,373 4 (Ilaims. (til. 1l282) This invention relates to animprovement in a fuze employing a dash-pot as a time delay unit.

Such a dash-pot when used in a wide range of temperatures due to thechange in viscosity of the fluid varies the delay period beyonddesirable limits. The type of dash-pot referred to is one in which thepiston head is fixed and the cylinder is moved by a constant force suchas a spring to press the fluid past the piston and the time required forthe cylinder to move is the time of the delay period. The time variesdepending on the viscosity of the contained fluid which in turn isdependent on the temperature. In a temperature range from 65 F. to +160R, where the fluid varies respectively from high to low viscosity, it isnecessary that the time delay unit operate in a range of 2.5 to 8.0seconds and the ordinary unit will not meet this requirement at thelower temperatures.

It is therefore the object of this invention to provide a dash-pot Whosecylinder moves past the piston head at a relatively constant rate ofspeed regardless of the temperature within the range of 65 F. to +160 F.

This object is accomplished by causing the cylinder to be moved by aconstant source of pressure, such as a spring, and the cylinder willonly move as fast as the fluid can flow through the clearance head andthe interior of the cylinder wall. However the fluid will have a lowviscosity at the higher temperatures and will flow more rapidly throughthe opening than at To compensate for this variation in viscosity, theclearance between the piston head and the cylinder wall is automaticallyadjusted with the change in temperature and viscosity. This change ofclearance occurs in such a ratio as to cause a relatively constant rateof movement of the cylinder past the piston head regardless of theviscosity of the fluid.

One way of properly varying the clearance to accomplish the desiredresults is to use a piston head that expands with the increase intemperature to provide a smaller clearance and contracts with areduction of temperature to obtain greater clearance. Such a piston headmay be made of a temperature sensitive hi -metallic flat strip coiled toform a piston head of circular shape and whose diameter or peripheryexpands or contracts with changes in temperature of the fluid to providea clearance that will permit an approximately constant flow of fluidpast the piston head regardless of the temperature and/ or viscosity ofthe fluid in the cylinder.

Reference is made to the drawings which will afford a betterunderstanding of the invention, in which FIGURE 1 is an enlarged sectionof the delay element employed with the fuze;

FIGURE 2 is a top View of the spider to depict its general shape;

FIGURE 3 is a diagrammatic representation of the apparatus controllingthe delay element, and

between the piston United States Patent ()fi ice FIGURE 4 is an enlargedsectional view of the piston head.

In FIGURE 1 the delay element which is the dash-pot is shown mounted onthe fuze body 10 and is contained in a housing 11. The dash-pot in thehousing 11 consists of a fuze activating-slider member 9 having acylinder 12 closed at one end with a member 13 having a peripheralflange l4 and a sealing member 15 forming a closure for the oppositeend. A spring 16, coiled around the outside of the cylinder 12, rests atone end on the interior of the housing 11 and is biased at the other endon the flange 1 to move the cylinder when the control apparatus isactivated. Centered within the cylinder 12 is a piston rod 1? whichpasses through the sealing member 15 and the housing 11, and ismaintained in a fixed position by the lock nut 18. A piston head 19 iskeyed to the free end of the piston rod 17 and is guided in the cylinder12 by the spiders 20 and 21 positioned on opposite sides of the pistonhead 19. The spiders 20 and 21 are circular discs having projections 34on the periphery that are spaced 90 apart and guide the piston head inthe cylinder. The space between the projections are segments 35 cut fromthe periphery which are adapted to provide the openings necessary forthe fluid to flow past the piston head. The portion of the opening thatis eflective for the passage of liquid is dependent on what part ofopening is left as the variable periphery of the bi-metallic coilchanges position with change of temperature and/or Viscosity of thefluid.

The annular piston head 19 is made of a flat bi-metailic strip coil likea spring and will expand and contract proportionately with changes oftemperature of the fluid 22 in the cylinder 12. The flat bi-metallicstrip is selected as being the material most sensitive to temperaturechange, thus a piston formed by wrapping bi-metallic strip about apiston rod and forming a coil will produce the desired result since thecoil will grow larger when heated and decrease in diameter when cooled,which produces an automatic change in clearance due to temperaturechange. Tests show that such a coil properly designed would compensatefor the change in fluid viscosity, due to change in temperature, to suchan extent that under a given load, the coiled piston head will movethrough the fluid at an almost constant rate regardless of thetemperature of the fluid. it is essential that as much metallic strip aspossible be Wound into any given diameter because the amount of reactionof the strip to temperature change is in direct proportion to the lengthof strip used. This change in diameter or periphery of the piston headgoverns the clearance between the piston head 19 and the cylinder 12 inaccordance with the changes in temperature and/or changes in viscosityof fluid 22 in the cylinder 12.

The fluid 22 is utilized to control the delay action of the dash pot andmust satisfy the requirements of remaining a true fluid at temperaturesranging from F to +160 F. and also remain fluid at F. when stored for 4years without deterioration. The following four silicone fluids with aviscosity of 100,000 cs. or higher will satisfy the necessaryrequirements:

Cs. viscosity (a) Dow Corning Fluid XF371 100,000 (b) Dow Corning FluidXF371 450,000 (0) Dow Corning Fluid 510 100,000

a General Electric Fluid ablilb'aiijjjj 400,000

Tests show these fluids are not adversely affected by storage at -80 F.nor do these fluids have a tendency in FIGURE .3 for the operation ofthe delay element in.

which no wiringis shown as the electrical connections Iform no part ofthis invention; the micro-switch 23 closes the circuit to activate thefiring solenoid 24 against the tension oi the spring 25 to withdraw thebore riding retaining pin 26 from the forked end 32 of the slider membet9; the slider member 9 and its cylinder 12 are then free to move and aremoved when the spring 16 is able to overcome theresistance offered bythe passage of the fluid 22 through the clearance between the pistonhead 19 and the cylinder 12 andthe time required to move the cylinder 12is the time delay desired for the operation of the fuze; the movement ofthe slider member 9 permits the angled edge 27 to depress the plunger 28carrying the member 29'which makes contact and activates the acro-switch3t). To determine the delay under various test conditions, a clock maybe started by the micro-switch 23 and stopped when the acro-switch isactivated. The delay element may be reset by releasing the resetsolenoid 31 to permit the reset plunger 32 to be moved by the spring 33against the plunger 28 which in turn bears against the angled edge 27 tomove the slider member 9 to its original position at the left againstthe tension of the spring 16, and when moved far enough, the deenergizedfiring solenoid 24 permits the bore riding pin 26 to return to theposition shown in FIGURE 3 by the force of return spring 25. I

While this particular embodiment of this invention is shown anddescribedwherein the cylinder 12 is the moving element or" the dash-potbut it should be noted that it is within the scope of this invention forthe cylinder 12 to be stationary and the piston rod 17 and the pistonhead 19 constitute the moving element of the dash-pot.

In theapparatus employed for tests, the best results were obtained whenthe clearance was varied from .005 to .026 inch when the cylinderslength was .468 inch and the extension of the cylinder was .540 inch.Results were as follows:

Time required for piston Temperature, F. to travel .18", sec.

These testsproved that this invention will permit the delay element tooperate within the desired limits regardless of the temperature and/ orviscosity of the fluid.

What is claimed is:

1. In a delay timing mechanism, the combination of a fuze bodycontaining a fuze and having a dash-pot mounted thereon, said dash-potbeing the delay element between firing and activation of the fuze andconsisting 1 of a housing containing a movable cylinder, saidcylinderhaving peripheral flanges at one end and containing a fluid sealedtherein, a coiled spring encircling said cylinder varied by temperaturechanges, said expandable periphery changing the clearance Withthecylinder to regulate the passage of fluid forced past the piston head bythe spring pressed cylinder when the firing solenoid is acti-- vated tocompensate for variations of'temperature and/ or viscosity to permit thedash-pot to operate Within a designed delay period'at any temperaturewithin the range of 65 F. to +160 F. and means for resetting themechanism.

2. In a delay timing mechanism, the combination of a 'fuze bodycontaining a fuze' and having a dash-pot mounted thereon, said dash-potbeing the delay element between firing and. activation of the fuze andconsisting of a housing containing a slider member movable within thehousing for-activating the title, said slider member having-at one endaforked portion-with a bore riding pin inserted in the base of the forkfor retaining said slider member, a resetting plunger protruding throughthe housing for contact with said slider member, said slider membcrprovided with an angled edge for contacting said resetting plunger, anopen-ended cylinder at the opposite end of the slider member adapted tobe received in' the dash-pot to form a closed container, said cylinderhaving peripheral flanges at the closed end and containing a suitablefluid sealed therein, a coiled spring encircling said cylinder bearingagainst the peripheral flanges at one end and biased against thehousing'at the other end, a piston within said cylinder having a pistonhead at one end and firmly keyed to the housing at the other end,spiders acting as closures on both sides of'said piston head, saidspiders having projections 90 apart at the periphery to guide the pistonhead in the cylinder, peripheral openings cut out between saidprojections adapted to provide passageways for fluid by the piston head,said piston head made of a coiled flat bi-metallic strip formand meansfor forcing said resetting plunger against the angled edge of the slidermember to return the'slider and the cylinder to the original position.

3. In a delay timing mechanism 'incorporatinga dash- V pot consisting ofa cylinder filled with a fluid, a piston bearing against theperipheralflanges at one end and biased against the housing at the other end, afiring solenoid connected to a bore riding pin retaining said cylinderagainst the action of the spring, a piston rod within said 4cylinderhaving a piston head at one end and firmly keyed to the housingat the other end, spiders acting as closures for both sides of saidpiston head andas guides for piston head in the cylinder, said pistonhead made of a coiled 1 ,flat bi-metallic strip forming an expandableperiphery within the cylinder having an annular piston head withawanable periphery adjacentthe cylinder wall and providing a clearancetherebetween, spiders having projections for guides on'both'sides ofsaid piston head and openings between projections for the passage offluid, said openings bounded at the periphery by the cylinder wall, saidpiston head formed of a coiled flatbi-metallic strip between the spidersand responsive to temperature changes of said fluid, the periphery ofthe coil changing with temperature changes to vary proportionately theeffective openings between said periphery and said cylinderwall togovern the flow of fluid past the piston-head.

whereby the time of the flow is approximately the same, regardless ofthe temperature of the contained fluid to assure the delay time iswithin desired limits. 1

4. In a delay timing mechanism'incorporating a dashpot, said dasl1-potcomprising a cylinder filled with fluid, a piston rod within thecylinder having a piston head at one end, spiders acting as closures onboth sides of said 7 piston head and having projections apart acting asguides for the piston head in the cylinder, openings formed by cuttingaway a portion of the peripheryof the spiders between said projectionsto provide passageways forfluid *by the piston head, said openingsbounded at the periphery by the cyiinder wall, said piston head" made ofa coiled flat bi-m'e'tallic strip having a variable periphery adjacentthe cylinder Wall and providing a clearance therebetween to control theeffective openings of the spiders, said variable periphery changing theclearance between the piston head and the cylinder to provide the onlypassageway for fluid by the piston head and to compen- 5 sateproportionately for changes in temperature and inversely proportional tochanges in viscosity of the fluid in the cylinder and said dash-potadjusting to fluid temperature and acting within the desired delay timeWhen the cylinder is operating With a fluid at any temperature 10 Withinthe range of 65 F. and +160 F.

References Cited by the Examiner UNITED STATES PATENTS 1,486,381 3/24Jaenichen 188-100 2,938,463 5/60 Jasse 10282 X 3,102,480 9/63 Severanceet a1. 10282 X FOREIGN PATENTS 1,115,057 12/55 France.

SAMUEL FEINBERG, Primary Examiner.

1. IN A DELAY TIMING MECHANISM, THE COMBINATION OF A FUZE BODYCONTAINING A FUZE AND HAVING A DASH-POT MOUNTED THEREON, SAID DASH-POTBEING THE DELAY ELEMENT BETWEEN FIRING AND ACTIVATION OF THE FUZE ANDCONSISTING OF A HOUSING CONTAINING A MOVABLE CYLINDER, SAID CYLINDERHAVING PERIPHERAL FLANGES AT ONE END AND CONTAINING A FLUID SEALEDTHEREIN, A COILED SPRING ENCIRCLING SAID CYLINDERLBE BEARING AGAINST THEPERIPHERAL FLANGES AT ONE END AND BIASED AGAINST THE HOUSING AT THEOTHER END, A FIRING SOLENOID CONNEDTED TO A BORE RIDING PIN RETAININGSAID CYLINDER AGAINST THE ACTION OF THE SPRING, A PISTON ROD WITH SAIDCYLINER HAVING A PISTON HEAD AT ONE END AND FIRMLY KEYED TO THE HOUSINGAT THE OTHER END, SPIDERS ACTING AS CLOSURES FOR BOTH SIDES OF SAIDPISTON HEAD AND AS GUIDES FOR PISTON HEAD IN THE CYLINDER, SAID PISTONHEAD MADE OF A COILED FLAT BI-METALLIC STRIP FORMING AN EXPANDABLEPERIPHERY VARIED BY TEMPERATURE CHANGES, SAID EXPANDABLE PERIPHERYCHANGING THE CLEARANCE WITH THE CYLINDER TO REGULATE THE PASSAGE OFFLUID FORCED PAST THE PISTON HEAD BY THE SPRING PRESSED CYLINDER WHENTHE FIRING SOLENOID IS ACTIVATED TO COMPENSATE FOR VARIATIONS OFTEMPERATURE AND/OR VISCOSITY TO PERMIT THE DASH-POT TOOPERATE WITHIN ADESIGNED DELAY PERIOD AT ANY TEMPERATURE WITHIN THE RANGE OF -65*F. TO+160*F. AND MEANS FOR RESETTING RANGE OF -65*F. TO +160*F. AND MEANS FORRESETTING THE MECHANISM.